1. Field of the Invention
The present invention relates to a laser processing device that condenses a beam emitted from a laser beam source, makes the condensed beam incident to an optical fiber, condenses the beam emitted from the optical fiber onto an object to be processed by a condensing optical system, and finely processes the object.
2. Description of the Related Art
Conventionally, there have been developed various kinds of laser processing devices that condense a laser beam emitted from a laser beam source onto an object to be processed, and carry out fine processing of the object such as welding, perforation, and cutting, or irradiation processing of the object.
To facilitate the utilization of this laser processing device, a laser micro-spot welding apparatus, for example, uses an optical fiber in the laser processing device for transmitting a laser beam, thereby to improve the flexibility in the structure of the device and reduce the weight of the device. A laser beam is transmitted to the vicinity of the object to be processed through this optical fiber.
The laser micro-spot welding apparatus using the optical fiber has a condensing optical system that condenses the laser beam transmitted to the vicinity of the object, onto the surface of the object to be processed. This condensing optical system is composed of a combination of a collimator lens and a condensing lens, or a combination of a collimator lens, a galvano-scanner, and an fθ lens.
This condensing optical system condenses the laser beam transmitted through the optical fiber, and forms a beam spot having a desired diameter on the surface of the object to be processed. This object is welded using the beam having this spot diameter.
In this laser micro-spot welding apparatus, the beam spot diameter (nugget diameter) is changed depending on a material of the object to be processed. As a method of changing this spot diameter, a distance between the focal point of the condensing lens or the fθ lens and the object to be processed is changed. It is possible to change the diameter of the spot diameter formed on the object, by changing this distance.
The above changing method, however, has the following problems.
(1) In order to change the diameter of the beam spot that is formed on the object to be processed, it is necessary to provide a special mechanism for changing the distance between the object to be processed and the condensing lens or the fθ lens.
(2) The fθ lens irradiates a beam onto the object approximately perpendicularly to the object, and slight error occurs at this time. When the distance between the object and the fθ lens is changed, there occurs a deviation in the position of the beam spot on the object.
Therefore, in carrying out a continuous spot welding by operating the galvano-scanner, it is necessary to re-define the X-Y coordinates of a galvano-head including the galvano-scanner, each time when a distance between the object to be processed and the fθ lens is changed along the Z axis as the optical axis.
The present invention has been made in the light of the above problems. It is, therefore, a first object of the invention to provide a laser processing device that does not require a special mechanism for changing a distance between a condensing lens and an object to be processed at the time of changing the diameter of a beam spot on the object.
It is a second object of the invention to provide a laser processing device using a galvano-scanner that does not require a re-definition of the X-Y coordinates of a galvano-head each time the diameter of a beam spot, on an object to be processed, is changed.